There are a number of automatic and semi-automatic rifles used by military personnel as well as law enforcement and civilians. While fully automatic rifles are generally illegal for use by the civilian population, many of the components which constitute an automatic rifle are the same as those found within semi-automatic models legalized for civilian use. Arguably the most popular semi-automatic assault-type rifle used by civilians, particularly within the United States, is the AR-15 and its clones. AR-15 is a registered trademark of Colt Industries. A number of additional companies manufacture clones of the AR-15 and market these clones under separate trademarks. While used throughout the specification, it is to be understood that the term AR-15 is meant to include not only those rifles manufactured by Colt Industries, but also those additional clones and any variants thereof. The AR-15 is the semi-automatic variant of the fully automatic M16 rifle used by United States military personnel.
The AR-15 and M16 are designed as modular rifles generally comprising a buttstock, lower receiver, upper receiver and barrel assembly. Each component is separable from one another and affords rifle owners the opportunity to customize the rifle with after-market components such as barrels of differing lengths, upper receivers designed to handle different calibers of ammunition, flashlights, hand guards, grenade or flare launchers, flash or sound suppressors, grips, and front or rear sights. To operate, the lower receiver is configured to include a fire control group (“FOG”) (generally a trigger, hammer, disconnector, and associated hardware including pins and springs) and a magazine box wherein activation of the FCG (by manipulation of the trigger) causes a round (bullet) housed within the chamber of the upper receiver to be fired out the barrel of the rifle by action of a reciprocating bolt carrier group housed within the upper receiver. Internal mechanisms of the upper receiver expel the shell casing of the fired round from the chamber while components engaged with the magazine box housed within the lower receiver feed a new round into the now-empty chamber. The buttstock mounts to the lower receiver and includes a buffer assembly and action (or recoil) spring in communication with the bolt carrier group. After a spent shell has been discharged, the spring urges the bolt carrier group back toward the chamber in preparation for firing another round.
The modular construction of these rifles enables generally quick and easy field-stripping (disassembly of the rifle for cleaning of the rifle to ensure proper firing of the weapon). In field-stripping the rifle, the lower receiver is separated from the upper receiver to gain access to the internal components (bolt, bolt carrier group, FCG and respective associated hardware) for cleaning and re-lubrication. When assembled, the upper and lower receivers are secured to one another through rear and forward extensions on the upper receiver fitting between corresponding sidewalls forming notches or grooves on the lower receiver. The forward sidewalls and extension are fitted with a pivot pin to prevent the forward halves of the receivers from separating. Similarly, the rear sidewalls and extension employ a takedown pin to secure the two receivers together. To field-strip the rifle, the takedown pin is sufficiently pushed out of the extension so as to enable the rear extension to lift out of the rear sidewalls thereby pivoting the lower and upper receivers about the pivot pin. The pivot pin can then be pushed out a sufficient distance so as to enable removal of the front extension from the front sidewalls and thereby completing separation of the lower receiver from the upper receiver.
After a rifle has been field-stripped, the FCG can be removed from the lower receiver for cleaning or to swap in a different/customized FCG. Swapping FCGs permits owners to modify the trigger “feel” of the rifle by modifying the smoothness of the trigger pull or the trigger pull weight. Removal of the FCG first requires the removal of the hammer pin which holds the hammer in place within the lower receiver. With the hammer and hammer spring removed, the trigger pin is removed from the lower receiver thereby freeing the trigger and disconnector for removal. Each of the removed parts may be cleaned or a new FCG may be selected for insertion into the lower receiver.
Replacing the FCG reverses the above steps such that the trigger and disconnector (with appropriate springs in proper position and orientation) is dropped into the lower receiver. The through-bores machined within the trigger and disconnector are aligned with one another and with the associated receiving openings fabricated within the lower receiver. The trigger pin is then slid through the one of receiver openings, the trigger/disconnector through-bores and finally the second receiver opening thereby capturing the trigger/disconnector within the lower receiver. The hammer (with properly mounted hammer spring) is then engaged with the trigger and disconnector with the hammer retained in place on the lower receiver by passing the hammer pin through the proper opening on the receiver and passing the hammer pin through the through-bore of the hammer. The length of the trigger pin and hammer pin are each selected so that each end of the pins will sit flush with the outer surface of the lower receiver when assembled.
In general, one leg of the hammer spring engages and rests within a groove formed within the trigger pin. The groove generally circumnavigates the pin so that if the trigger pin should rotate the hammer spring will remain within the groove. The leg of the hammer spring resting within the trigger in groove prevents walking (lateral displacement) of the trigger pin out the side of the lower receiver. However, if the groove becomes worn or should the hammer spring leg otherwise disengage from the trigger pin groove, the trigger pin may walk laterally (particularly when subjected to the oscillatory impacts associated with firing a semi-automatic rifle) leading to a non-functional weapon and a dangerous and potentially fatal situation. It is also possible for the trigger pin to fail and fracture, particularly at the groove where the pin has a smaller diameter.
A number of solutions have been proposed to alleviate the possibility of trigger pin walking and/or fracturing. For instance, one proposed solution has been to extend the length of the trigger pin and/or hammer pin so that one or both ends of the pin protrude from the outer surface of the lower receiver. The protruding ends are then secured with a clip, such as a c-clip, such that the c-clips prevent the pin from traveling laterally. While this solution may arguably prevent pin walking, the extended pin length and clips present alternative problems. Primarily, the extended pin and clips may interfere with the rifle operator, particularly if wearing gloves which may snap the end of the pin or the clip. An operator may also be cut by the sharp edge of the pin or on a point of the clip. This cut may hinder firing of the rifle if that cut happens to be on the operator's trigger finger where the cut can cause discomfort as the injured finger applies the necessary trigger weight to fire the rifle.
A further, similar approach does not extend the pin or add a clip, but rather employs a headed fastener passing though the lower receiver to engage the pin while the head rests outside the outer surface of the lower receiver. This approach has the trigger pin and/or hammer pin of the same nominal width of the originally supplied pins. However, this solution modifies those pins so that each end of the pin is adapted to carry a threaded bore. Once properly inserted into the lower receiver, each end of the pin is capped with a respective cap screw with the screw head resting outside of the lower receiver to prevent pin walking. Ideally, the cap screw seats against the pin and not against the lower receiver. In this manner, the pin is allowed to rotate thereby minimizing wear on the pin (and thus minimize the potential for pin fracture). However, as the heads of the cap screws extend outside the outer surface of the lower receiver, this solution presents the same drawbacks as those of the clip as discussed previously.
As such, there is a need for an anti-walk pin assembly for use with a lower receiver assembly which secures the trigger pin and/or hammer pin within the lower receiver without hindering operator use of the rifle. The present invention addresses these and other needs.